In the field of brush cutting using a riding type machine such as a tractor, conventional machines use a blade assembly which generally includes two blades, each blade having two ends with a double sided cutting edge on one end. In one form of the prior art, a crossbar is used also having two ends, each end having one position for attaching a blade to the crossbar. One blade is attached at the bottom surface of the crossbar at one end of the crossbar with the blade in use presenting a forward facing blade to the material to be cut. A similar blade is attached at the other end to the bottom surface of the crossbar with a rearward facing blade presented to the material to be cut. As the crossbar rotates around a horizontal plane, the blade having the rearward facing cutting edge moves into the position of the forward facing cutting edge so that the two blades cut the material in a circular fashion. At the attachment position where the prior art blade attaches to a crossbar there is no cutting edge. The prior art blade then is turned over when the cutting edge on one side is dulled and the second cutting edge is used. In the prior art, a bolt is positioned through a hole in the distal end of the blade and into a corresponding hole in the crossbar. A nut is attached to the bolt at the top of the crossbar thus attaching the blade to the crossbar. During brush cutting, as the blade is presented to the ground, the head of the bolt protrudes from the bottom surface of the blade. In another form of the prior art, a pair of reversible blades are attached to the top surface of the crossbar thus requiring a stop mechanism so that as the blades rotate they do not strike the drive shaft that attaches the blade assembly to the boom of the cutting machine. In an alternate embodiment of the prior art, there is an offset in the form of a curve in the blade which allows the blade to be presented closer to the ground than the generally flat blade to thereby provide a closer cut. There are a number of problems in the prior art blade assemblies used for brush cutting. With the double sided cutting edge on one end there are only two useable cutting surfaces on each blade. The prior art blade is not resharpenable so that once the two cutting edges have been dulled the blade must be permanently replaced. These cutting surfaces are dulled rather quickly requiring much maintenance and expense to replace the blade. Further, with the nut and bolt attachment of the blade to the crossbar in the prior art, the head of the bolt protrudes from the lower surface of the blade. The lower surface of the blade is presented to the ground during brush cutting and when the blade strikes a rock or the like, hitting the head of the bolt, the bolt will most often be chipped, compromising the integrity of the bolt. This suggests a possible dangerous situation if the blade were to become unattached from the crossbar, and requires frequent replacement of the bolt with corresponding maintenance and expense.
U.S. Pat. No. 1,622,611 to Sera discloses a lawn mower with blades that rotate in a horizontal plane to cut grass in a circular path.
U.S. Pat. No. 2,786,322 to McEvers discloses a power mower rotary blade with four cutting edges that is horizontally rotatable so that two different sets of blades can be used in rotary operation. The blades are attached to a cutter bar using countersunk screws.
U.S. Pat. No. 3,395,522 to Zweegers teaches a mowing machine which includes a rotatable cutting device having drums with multiple blades attached that roll along the ground to cut grass, hay or the like.
U.S. Pat. No. 3,507,104 to Kline et al discloses a knife mounting for a rotary mower whereby two knives on one cutter can be removed and substituted for two knives on an adjacent rotor so more knives can be used in the field before the knives are resharpened.
U.S. Pat. No. 3,762,138 to Michael discloses a mower blade assembly with cutter elements removably attached to a blade bar with flush mounted attachment pins.
U.S. Pat. No. 4,611,459 to Cartner discloses a blade assembly having four cutting edges, whereby the blade is attached to the upper surface of the crossbar. This configuration requires a stop mechanism so that as the crossbar rotates, the blades do not cut through the drive shaft that connects the blade assembly to the boom of the cutting machine.
U.S. Pat. No. 4,9222,698 to Taylor discloses a cutter bar for a rotary lawn mower which has a plurality of indexable blades, whereby the cutter bar may be replaced without removing the blades or up-ending the mower.